Process for the treatment of hydrocarbon oil



Sept. 14, 1937. P. c. KEITH, JR 2,093,278

PROCESS FOR THE TREATMENT OF HYDROCARBON OIL I I Filed Oct. 5, 1953INVENTOR A'ITORNEY Patented Sept. 14, 1937 FATENT @FHQE PROCESS FOR THETREATMENT OF HYDROCARBON 01L Percival 0. Keith, Jr., Peapack, N. 5.,assignor to Gasoline Products Company,

Inc, Newark,

N. J a corporation of Delaware Application October 5,

3 Claims.

This invention relates to processes for converting relatively highboiling hydrocarbon oils into lower boiling products, particularlygasoline.

It is an object of my invention to provide a plural section crackingunit, one section of which is adapted to make from relatively heavy ordirty charging stock a clean charging stock for cracking in anothersection.

The above mentioned and further objects and advantages of my inventionwill be made clear in the following description taken in conjunctionwith the accompanying drawing.

Referring more particularly to the drawing, fresh charging stock forexample, topped crude or other relatively heavy hydrocarbon oil, isforced by pump i through charging line 2, preheating coil 3, heatexchanger 4, heat exchanger 5, and branch lines 6 and 1, into anintermediate section in combination tower 8, wherein it is contactedwith highly heated vapors rising through the tower, as will be explainedmore fully hereinafter, The amount of oil introduced through the pipe Iis preferably only that sufficient properly to reflux the baiile plates9, while the remainder is introduced through pipe 6, the valves til andIl serving as control means. The unvaporized portions of the freshrelatively heavy charging stock are collected on trap out tray 2 withthe condensed portions of the hot vapors rising through the tower, andwithdrawn through pipe 13 into accumulator drum M, from which they arepassed through pipe I5 by pressure pump it into heater H, which ispreferably of the tubular type. The oil is raised to a crackingtemperature in the heater ii, and may undergo some conversion therein,emerging at a temperature of from 800 to 900 F., for example about 856F. This hot oil passes through pipe i8 into reaction chamber i9, whereinfurther conversion thereof takes place without additional heating. Thisreaction chamber is preferably vertically disposed, the line 18connecting at the top thereof. If desired the heater ll may be sooperated as to cause therein part, or all, of the desired cracking ofthe charging stock, or only a very small portion of the cracking may beaccomplished in the heater, and the rest may take place in the reactionchamber l9. Preferably a considerable portion of the cracking takesplace in both the heater and the reaction chamber, the total crackingper pass amounting to possibly 12-13%, although the percentage ofcracking may be less or more than that mentioned, depending on the stockbeing treated, this being in the nature of a viscosity breakingoperation. The pressure on the oil in 1933, Serial No. 692,237 a (Cl.l-48) the reaction chamber is preferably of only a moderate value, e. g.225 pounds per square inch, this being preferably substantially the sameas the heater outlet pressure, although pressures from atmospheric to480 pounds per square inch may be used in both heater and reactionchamber. It is generally desirable however, to operate considerablybelow the 400 pound value in order to prevent the deposition of largeamounts of coke.

The cracked products pass oil from the reaction chamber through pipe 29and reducing valve 2i, into a lower section "i2 in the combination tower8, under a pressure preferably considerably lower than that in thereaction chamber, e. g. 45 pounds per square inch, although pressuresfrom atmospheric to pounds per square inch, or more, may be used ifdesired, the main requisite being that the pressure be lower than thatin the reaction chamber, so that flashing takes place by the containedheat of the hot products. In the combination tower 8 the introducedcracked products separate by their contained heat into vapors which riseupwardly through the tower, and liquid residue which collects on trapout tray 22. The highly heated vapors rising upwardly through the towerserve to strip the fresh charge introduced through pipes 6 and l oflighter products in the nature of gas oil, kerosene, and the like, theselighter products rising in vapor form past the baffle plates 9, bubbletrays 23, and trap out tray 24, upon which the heavier portions thereofcondense, while the lighter vapors move upwardly past bubble trays 25,heat exchanger coil 3, and bubble trays 26. The vapors which reach thetop of the tower pass off through vapor line 2'5, and condenser 28, intoreceiving drum 2E3 having the usual gas draw off line 29 and liquid drawoff line 38f, these vapors being of the boiling range desired for thefinal product, e. g. gasoline. Some of the distillate collecting in thedrum 29, may be pumped back in the usual manner through line 33 by pump3! to serve as reflux in the top of the tower. The condensate collectingon the trap out tray 25 is so selected as to be suitable for use asclean cracking stock and this clean condensate product, which may, forexample, comprise light gas oil and kerosene, is drawn off through line32 and heat exchanger 4, into accumulator 33, from which it is withdrawnthrough conduit 35 and forced by pump 36: through line 3'! and heatexchanger 38, into an intermediate point in combination tower 539. Aportion of the liquid product from accumulator 33 is forced through line48, having branches 4! and 42, to serve as reflux on the bubble trays 23and 25 respectively, valves being provided to effect the necessarycontrol. A portion of this lightly cracked product, e. g., gas oil, maybe drawn off through line 43 and cooler 44, into storage drum 55, foruse as Diesel oil, or for any other purpose, the necessary control beingeffected by valve 46. In the combination tower 39 the introduced cleancondensate stock flows downwardly over balile plates 47 against anupwardly rising current of highly heated vapors, with the result thatthe condensate is highly heated. A portion of this condensate may bevaporized. The unvaporized portions of the introduced clean condensate,mixed with the condensed portion of the rising vapors are collected ontrap-out tray t8 and withdrawn through pipe 49 into accumulator 50. From50 the condensate is withdrawn through pipe 5| and forced by pump 52through cracking heater or furnace 53, which is preferably of thetubular type, being raised in temperature, by passage through theheater, to a rapid cracking temperature, preferably about 900 F. andunder a pressure of a relatively high value, preferably about 750 poundsper square inch, although somewhat higher or lower temperature and/ orpressure may be used. The temperature may range, for example, from 850to ll00 FL, while the pressure may be several hun dred pounds higher orlower than that mentioned as preferred, the values selected dependinglargely upon the character of the charging stock and the particularfinal products which it is desired to produce. From the furnace thehighly heated cracked products pass through conduit 54 into reactionchamber 55, which is preferably verti-- cally disposed, the line 5entering the top thereof. The crackingper is preferably considerablyhigher than that taking place in the heater H, and may be, for example,in the neighborhood of 18% to 20%, although the value may be higher orlower than that mentioned, depending upon the character of the chargingstock and the particular conditions selected for operation. The majorportion of the cracking preferably takes place in the reaction chamber55, a part only being effected in the heater 53, although the proportionof cracking in the heater with respect to that taking place in thereaction chamber may be altered as desired by varying the time ofpassage of the oil through. the heater and the temperatures to which itis subjected therein. From the reaction chamber 55 the cracked productspass through pipe 55 and reducing valve 51, into the lower part'fia ofcombination tower 39, which is maintained at a pressure considerablylower than that in the reaction chamber 55, being, for example, in theneighborhood of 240 pounds per square inch. This value is given by wayof illustration and approximates that preferred in most cases, althoughhigher or lower pressure may be used, depending upon the amount oflighter products which it is desired to separate from the cracked oilintroduced into the combination tower from the reaction chamber. Thelower the pressure in the combination tower, the greater the amount oflight products flashed off. The line 56 preferably withdraws oil fromthe lower part of reaction chamber 55, and in order to preventaccumulation of coke around the point of connection of line 56 with thereaction chamber, and also to prevent the accumulation of coke in theline 56, a portion of the combined feed forced by the pump 52, may bediverted through cross-over line I! into the lower portio-n of thereaction chamber, slightly above the point of connection of the line 56,the amount of oil so introduced being sufficient to agitate and flushout any accumulating carbonaceous matter, the control being effected byvalve 18. The amount of oil so by-passed through line Tl should besufficient to keep the temperature in the lower part of the reactionchamber down. to a value of approximately 800 F., more or less. Thelower portion 58 of this combination tower constitutes an evaporator orseparator. The evolved vapors pass upwardly through trap-out tray 48,baffles 41 and bubble trays 59, encountering downwardly flowing streamsof reflux condensate, and fresh charge introduced through pipe 31, withthe result that heavier fractions of the rising vapors are con,

densed and collected on the trap-out tray 48 with unvaporized portionsof the fresh charge, to be recycled through the heater 53 and furthercracked. The vapors remaining uncondensed at the top of the uppersection 60 of combination tower 39; which acts as a ,dephlegmator orfractionator, pass off through vapor line 6|, heat e-x-' changer 38,wherein partial cooling is effected, and final condenser 62, intoreceiving drum 63,- which is provided with the usual gas draw-off pipe64, and liquid draw-off pipe 65. A portion of the distillate may bepumped back from the drum 63 through pipe 06, by action of pump 61, toserve, in the well-known manner, as a refluxing medium in the top of thetower. This distillate so collected will have the characteristics of thefinal desired product, and if desired may be blended with that collectedin. drum 29, by opening valve 68 in cross-over line 69. Liquid residueremaining unvaporized in the bottom of evaporator section 58 ofcombination tower 39, may be drawn off from the system in part orwholly, through line 16, but is preferably passed throughconduit 10,having reducing valve H, into the lower portion 12 of combination tower8, which serves as a flash drum for flashing off the lighter productsfrom the residue. drum 12 is aidedsomewhat by the contacting of theresiduewith the highly heated products from the reaction chamber [9. Theaction is further aided by the fact that both liquid residue and crackedproducts from reaction chamber l9 are preferably introduced below thelevel of the liquid on the tray 22. Excess oil accumulating on the trayoverflows the top thereof and passes downwardly through tower 8, fromwhich it. is withdrawn through draw-off line 13, heat exchanger 5, andcooler 14, to fuel oil storage drum 15.

The quantities of stock flowing through the various. pipes of a.combination unit such as disclosed herein, will, of course, vary bothwith the amount of fresh charge introduced into the system and with thespecific conditions set up in the several sections of the systems,however, the following figures set forth one successful set of operatingconditions.

Assuming the fresh charge to be 26 A. P. I. topped Persian crude, thisbeing the remaining 60% after 40% of the original crude has beendistilled off, the temperature of the oil at the point of introductioninto combination tower 8 through pipes 6 and I, after preheating in coil3 and exchangers 4 and 5, may be about 575 F., and the pressure thereonmay be about 45 pounds per square inch. The oil withdrawn from trap-outtray I2 may have a temperature of .700" F., and its temperature afterleaving the heater I! may be about 850 F. the pressure be- The flashingprocess in flash ing 225 pounds per square inch or thereabouts. Underthese conditions a cracking to products in the gasoline boiling range,per passage of the oil through the heater I1 and reaction chamber I9,may be about 12 to 13%, the amount of oil passing through the heater I!being about double that of the fresh charge introduced through pipe 2,and comprising, for example, one part of topped crude and one part ofheavy gas oil. The temperature at the top of the combination tower 8 maybe about 375 F., and the percentage of gasoline passed to the receiver29, with respect to the amount of fresh charge through pipe 2, may beabout 20 to 25. The fuel oil withdrawn from the bottom of thecombination tower through conduit 13 may constitute about 45 to 50% withrespect to the fresh charge, this residue being a tar having a gravityof 13 to 14 A. P. I., for example. Gas oil to the extent of may bewithdrawn through line 43 to storage, while the amount of cleancondensate introduced into the combination tower 39 through pipe 31 may,in amount, approximate 38% with respect to the fresh charge. Thetemperature in the base of combination tower may be about 750 F. and thepressure about 240 pounds per square inch, while the temperature andpressure in the reaction chamber 55 may be about 900 F. and 750 poundsper square inch. The temperature of the vapors at the top of thecombination tower 39 may be about 450 F. and the quantity of gasolinecollected in the receiver 63 may be about 15 to with respect to thequantity of the fresh charge through line 2.

Operation In operation fresh charge, such as topped crude, cruderesiduum, or even heavy distillate, is introduced through the chargingline 2, preheating coil 3, heat exchangers 4 and 5, and pipes 6 and 1,into an intermediate point in the combination tower 8, the amount offresh charge introduced through pipe I being sufficient for refluxingthe baffles 9 and maintain the proper temperature, while the remainderis directed through pipe 6 onto the trap-out tray l2. The introduced oilis stripped of its lighter fractions by its contained heat resultingfrom its preheating, and as a result of the contacting there- I of withrising highly heated vapors in the tower 8. The evolved vapors passupwardly countercurrent to downwardly flowing reflux condensate, withresulting condensation of heavier fractions of the vapors. Thosefractions remaining uncondensed at the top of the tower pass off outtray 24, and the treatment thereof will be explained more fullyhereinafter. This condensate may be, for example, a gas oil of about 36A. P. I. gravity.

The unvaporized portion of the fresh charge and condensed portions ofthe rising vapors are collected on trap-out tray l2, and withdrawn toaccumulator M, from which they are forced through pipe 15 and heater orfurnace ll, wherein the oil attains a temperature preferably falling inthe range of 800900P F., suitably about 850 F. under a pressure whichmay vary considerably, e. g. from a few pounds per square inch toseveral hundred pounds per square inch, preferably about 225 pounds persquare inch, and may be subjected to a certain amount of cracking also.The highly heated products then pass into reaction chamber l9 whereinfurther moderate cracking thereof takes place, this being in the natureof a viscosity breaking operation, wherein the total cracking toproductsin the gasoline boiling range may be from 8% to 15% per pass,preferably about 12-13%. The prodnets of conversion then pass throughpipe 20 and reducing valve 2i, into the lower part of the combinationtower 8, wherein, due to the reduc tion of pressure to a relatively lowvalue, separation of the cracked products into vapors and liquid residueresults, the vapors rising upward- 1y through trap-out tray l2 againstdownwardly flowing charging stock introduced through pipe I, withattendant condensation of the heavier fractions of the vapors. Theliquid residue collecting on tray 22 is, in effect, reboiled by the hotproducts introduced by pipe 20, the product remaining in liquid formoverflowing the trapout tray into the base of the tower, from which itis removed as fuel oil through pipe 13 and heat exchanger 5, serving toaid in preheating the fresh charge.

The clean condensate removed from trap-out tray 24 is subjected to heatexchange with the fresh charge in heat exchanger 4, andthence passesinto accumulator 33 from which it is withdrawn, through pipe 36, andforced through line 31 and heat exchanger 38, into an intermediate pointin the combination tower 39, another portion of this condensate beingreturned through line 40 to tower 8 as reflux, and a third portion beingremoved if desired through exchanger 38 for use as. Diesel oil, or asany other product. In the combination tower 39 the introduced cleancondensate is partially vaporized by contact with the highly heatedvapors, the portion remaining uncondensed being collected on trap-outtray 48 with condensed fractions of the rising vapors. This condensateconstitutes the charging stock for cracking furnace 53 and duringpassage 'therethrough is raised to a cracking temperature of, forexample, 850-1000 F'., preferably about 900 F., under a pressure, forexample, of from 200 to 1000 pounds per square inch, preferably about750 pounds per square inch, thereafter being introduced into thereaction chamber 55, a considerable portion of cracking taking place inthe furnace 53, or not, as desired. In the reaction chamber 55 furtherconversion takes place, the total amount of cracking being preferably asgreat as possible without deleterious coking. The cracking to productsin the gasoline boiling range, per pass, may range from 15 to 40%, forexample, depending on the character of the stock being treated, but ispreferably in the neighborhood of 18-20% per pass. The highly heatedcracked products are then introduced through pipe 55, into the lowerpart 58 of combination tower 39, with attendant reduction of pressure,by action of valve 51, sufficient to cause self vaporization of a largeportion of the cracked products. Flushing oil may be introduced throughcross-over line 11 into the lower part of the reaction chamber 55 to anextent of, for example, about 5% with respectto the amount of stockcharged to the heater 53. The vapors rise upwardly past the trap-outtray 48 and undergo partial condensation by contact with the downwardlyflowing charging stock introduced through line 31. The vapors remaininguncondensed are then subjected to fractionation by passage upwardlythrough the bubble trays or similar devices 59, to which a refluxingmedium is supplied through pipe 66. The vapors still uncondensed at thetop of the tower pass off through pipe 6|, are cooled in heat exchanger38, finally condensed in condenser 62 and collected in receiving drum 63as a desired product. This may be blended if desired with that productcollected in receiving drum .29, by opening valve 68 in cross-over pipe69. Liquid residue is withdrawn from the bottom of combination tower 39,and part or all thereof may be diverted from the system through pipe 16,but this residue is preferably passed through pipe Ill and reducingvalve 'll, into the flashdrum portion 12 of combination tower 8,wherein, due to the reduction in pressure thereon and the contactingthereof with highly heated products from pipe 20 partial vaporizationresults, the vapors passing upwardly through trap-out tray I2, Whileunvaporized liquid or residue overflows the tray 22 into the base of thetower. The; heavier portions of the rising Vapors are condensed andcollected on trap-out tray l2 and are recycled through the heater l1along with heavier fractions condensed from the vapors evolved fromstock introduced through pipe '20, while the unvaporized residue may bewithdrawn continuously or intermittently from the base of the tower,through pipe 13. The character of this residue may be varied as desiredby properly selecting the drop in pressure between towers 39 and 8, andthe other operating condition. This product is preferably withdrawn insuitable condition for use as fuel oil.

The unit described hereinbefore is very flexible and can be used tocarry out other processes than those specifically discussedhereinbefore, for example the unit may be used for reforming naphtha. Nochanges in the equipment are necessary to accomplish this end. The highpressure side of the unit may be used-with normal flow throughout asdescribed hereinbefore, while the low pressure tower 8 may be used forflashing the tar from the high pressure tower 39, the low pressurefurnace l1 and reaction chamber [9 then being unused. The naphtha mayberaised advantageously to somewhat higher temperatures than that used incracking gas oil, e. g., 950 F. or more in the heater 53 and then passedto the reaction chamber 55, the total amount of cracking per pass beingapproximately the same as in the case of gas oil. Approximately the samepressure may be used onthe reaction chamber 55 and combination tower 39,i. e. 750 pounds and 240 pounds respectively.

While I have described a particular embodiment of my invention for thepurpose of illustration, it should be understood that variousmodifications and adaptations thereof may be made within the spirit ofthe invention as set forth in the appended claims.

I claim:

1. The process of treating hydrocarbon oil that comprises subjectingcondensate oil in a cracking zone to cracking temperature undersuperatmospheric pressure to effect cracking, directing resultantproducts of the cracking into a separating zone maintained undersuperatmospheric pressure wherein separation of vapors from liquidresidue takes place, subjecting vapors thus separated to fractionationin a fractionating zone to separate out a desired light distillate and aheavier reflux condensate, directing reflux condensate so formed to saidcracking zone, passing liquid residue from said separating zone into aflashing zonev of, lower pressure wherein separation of vapors fromresidue takes place, passing vapors thus separated into a primaryfractionating zone separate from the first-mentioned fractionating zone,introducing charging stock of the nature of crude residuum into saidprimary fractionating zone to cause partial condensation of the vaporsand eifect partial vaporization of said charging stock, withdrawingunvaporized portions of said charging stock together with resultantcondensate from the primary fractionating zone, subjecting the admixedunvaporated charging stock and condensate in a separate cracking zone tocracking temperature under superatmospheric pressure to eflect cracking,directing, resultant products of cracking into said flashing zone toeffect separation thereof into vapors and residue, subjecting vaporsremaining uncondensed in said primary fractionating zone to furtherfractionation to separate out reflux condensate and combining refluxcondensate so formed with aforesaid condensate passing to thefirst-mentioned crackingzone. l

2. The process of treating hydrocarbon oil that comprises subjectingcondensate oil in a cracking zone to cracking temperature undersuperatmospheric pressure to effect cracking, directing resultantproducts of the cracking into a separating zone maintained undersuperatmospheric pressure wherein separation of vapors from liquidresidue takes place, passing separated vapors into fractionating zoneand subjecting them to fractionation therein to separate out a desiredlight distillate and a heavier reflux condensate, directing refluxcondensate so formed to said cracking zone, passing liquid residue fromsaid separating zone into a flashing zone of lower pressure whereinseparation of vapors from residue takes place, passing vapors thusseparated into a primary fractionating zone separate from the firstmentioned fractionating zone, introducing charging stock of the natureof crude residuum into said primary fractionating zone to cause partialcondensation of the vapors and efiect partial vaporization of saidcharging stock, withdrawing unvaporized portions of said charging stocktogether with resultant condensate from the primary fractionating zone,subjecting the admixed unvaporized charging stock and condensate in aseparate cracking zone to cracking temperature under superatmosphericpressure to effect cracking, directing resultant products of crackinginto said flashing zone to effect separation thereof into vapors andresidue, passing vapors remaining uncondensed in said primaryfractionating zone to a secondary fractionating zone, subjecting thevapors therein to fractionation to separate out a desired distillate andheavier reflux condensate and directing refluxcondensate so formed tosaid first mentioned fractionating zone.

3. The process of treating hydrocarbon oil that comprises subjectingcondensate oil in a cracking zone to cracking temperature undersuperatmos pheric pressure to effect cracking, directing resultantproducts of the cracking into a separating zone maintained undersuperatmospheric pressurewherein separation of vapors from liquidresidue takes place, subjecting. vapors thus separated to fractionationin a first fractionating zone to separate out a desired lightdistillate, passing liquid residue from said separating zone into aflashing zone of lower pressure wherein separation of vapors fromresidue takes place, passing vapors thus separated into a primarysection of a second fractionating zone, introducing charging stock ofthe nature of crude residuum into said primary section of the secondfractionating zone to cause partial condensation of the vapors andeffect partial vaporization of said charging stock, withdrawingunvaporized portions of said charging stock together with resultantcondensate from the primary section of the second fractionating zone,subjecting the admixed unvaporized charging stock and condensate in aseparate cracking zone to cracking temperature under superatmosphericpressure to effect cracking, directing resultant products of crackinginto said flashing zone to effect separation thereof into vapors andresidue, passing vapors remaining uncondensed in said primary section ofthe second fractionating zone to a secondary section thereof, subjectingthe vapors therein to fractionation to separate out a desired distillateand a heavier reflux condensate and utilizing reflux condensate soformed 10

